Osbornoceras is a genus of Lower Silurian cyrtoconic nautiloid cephalopods known from Ohio and possibly Manitoba, one of five general currently included in the oncocerid family Karoceratidae.

Osbornoceras grew to be somewhat large and is characterized by a narrow, compressed, strongly curved, exograstric shell.

Connecting rings are thin, septal necks cyrtochoanitic (outwardly flared).

Karoceras, from Europe and Russia, which followed in the Middle Silurian, is similar in overall form but is actinosiphonate.

Also similar is the closely related Lower Devonian Ankyloceras and earlier Middle and/or Upper Ordovician oncoceratids such as Diagenoceras and Richardsonoceras.